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Group no. 01
Rana Ahmed (PHA-14001)
Mahfujul Hasan (PHA-14002)
Shahida Yeasmin Sima (PHA-14005)
Shamima Akter Sumi (PHA-14007)
14 April 2019 1
Introduction to Pathology
Father of Modern Pathology
Cellular Injury and Adaptation
Stages of the cellular response
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What Is Pathology
• Pathology is the study (logos) of diseases (pathos).
• The study of the structural, biochemical and functional changes in
cells, tissues and organs that underlie diseases.
• It attempts to explain sign and symptoms by use of
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Father of Modern Pathology
“Virtually all forms of tissue injury
starts with molecular or structural
alterations in CELLS”
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The Scope of Pathology
Scientific knowledge about human diseases from observations on
patients or by from experimental studies.
Explain the whys and wherefores of signs and symptoms expressed.
It offers clinical care and therapy.
It serves as the bridge between basic sciences and clinical medicine.
Pathology is the foundation for all medicine.
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Core aspects of pathology
There are four aspects of diseases process that form the core of
pathology. These are following-
3. Molecular and morphological changes
4. Clinical manifestations
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Mechanism of its
Sequences of events in the
response of cells or tissues
to the etiologic agents.
from the initial stimulus to
the ultimate expression of
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Molecular and Morphologic
changes refer to the
structural alterations in
cells or tissues that are
either characteristic of a
disease or diagnostic of an
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The end results of genetic,
biochemical and structural
changes in cells and tissues
abnormalities, which lead
to the clinical
and signs) of disease, as
well as its progress.14 April 2019 10
Stages of the Cellular Responses
Fig: Stages of the cellular response to stress and injurious stimuli
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Adaptations are reversible changes in the size, number, phenotype,
metabolic activity or functions of cells in response to changes in their
Four types of adaptation are occurred-
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• Hypertrophy is an increase in the size of cells resulting in an increase
in the size of the organ.
• There are no new cells, just large cells.
• Hypertrophy can be physiologic or
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Cardiac enlargement that
occurs with hypertension
or aortic valve disease.
Bulging muscles of bodybuilders.
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Enlargement of the uterus during pregnancy
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Mechanisms of Hypertrophy
Hypertrophy is the result of increased production of cellular proteins.
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• Hyperplasia is an increase in the number of cells in an organ or
tissue, resulting in increased mass of the organ or tissue.
• Hyperplasia can be physiologic or pathologic.
• In both situations, cellular proliferation is stimulated by growth
factors that are produced by a variety of cell types.
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1. Hormonal hyperplasia:
The proliferation of the glandular epithelium of
the female breast at puberty and during
2. Compensatory hyperplasia:
When part of a liver is resected, mitotic activity in
the remaining cells begins as early as 12 hours
later, eventually restoring the liver to its normal
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Most forms of pathologic hyperplasia are caused by excesses of
hormones or growth factors acting on target cells.
Endometrial hyperplasia is an example of abnormal hormone
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Mechanisms of Hyperplasia
Hyperplasia is the result of growth factor, driven proliferation of
In some cases, by increased output of new cells from tissue stem
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• Atrophy is reduced size of an organ or tissue resulting from a
decrease in cell size and number.
• Atrophy represents a reduction in the structural components of the
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Common Causes of Atrophy
Loss of innervation
Diminished blood supply
Loss of endocrine stimulation
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Mechanisms of Atrophy
Atrophy results from decreased
protein synthesis and increased
protein degradation in cells.
Reduction metabolic activity.
Nutrient deficiency activates
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• Metaplasia is a reversible change in which one differentiated cell type
is replaced by another cell type.
• The most common epithelial metaplasia is columnar to squamous, as
occurs in the respiratory tract in response to chronic irritation.
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Mechanisms of Metaplasia
• Reprogramming of stem cells that are known to exist in normal
• The precursor cell differentiated along a new pathway, signaled by
cytokines, growth factor and components of the cell in this
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• If the adaptive capability is
exceeded or if the external
stress is inherently harmful or
excessive, cell injury develops.
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Causes of Cell Injury
• Oxygen Deprivation
• Physical Agents
• Chemical Agents and Drugs
• Infectious Agents
• Immunologic Reactions
• Genetic Derangements
• Nutritional Imbalances
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Biochemical mechanisms of cell injury
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Pathologic Effects of Free Radicals
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• Apoptosis is a pathway of cell death that is induced by a tightly
regulated suicide program in which cells destined to die activate
enzymes that degrade the cells own nuclear DNA and nuclear and
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CAUSES OF APOPTOSIS
Apoptosis in Physiologic Situations
Apoptosis serves to eliminate cells that are no longer needed and to
maintain a steady. It is important in the following physiologic situations:
The programmed destruction of cells during embryogenesis
Involution of hormone-dependent tissues upon hormone
Cell loss in proliferating cell populations
Elimination of potentially harmful self-reactive lymphocytes
Death of host cells that have served their useful purpose
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Apoptosis in Pathologic Conditions
Apoptosis eliminates cells that are injured beyond repair without
eliciting a host reaction, thus limiting collateral tissue damage.
Accumulation of mis-folded proteins
Cell death in certain infections
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MORPHOLOGIC AND BIOCHEMICAL
CHANGES IN APOPTOSIS
• Cell shrinkage
• Chromatin condensation
• Formation of cytoplasmic blebs and
• Phagocytosis of apoptotic cells by
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• Necrosis is a form of
cell death in which
fall apart and cellular
enzymes leak out and
ultimately digest the
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• Under some circumstances, cells may accumulate abnormal amounts
of various substances, which may be harmless or may cause varying
degrees of injury.
• The substances fall into two categories:
Normal cellular constituents
ex: Water, lipids, proteins etc.
ex: Products of infectious agents, abnormal
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Mechanisms of intracellular
1. Abnormal metabolism
2. Mutations causing
alterations in protein
folding and transport
3. A deficiency of critical
4. Inability to degrade
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Various components of intracellular
A. Depositions of lipids
a. Fatty change
b. Cholesterol deposition
B. Deposition of proteins
C. Deposition of glycogens
D. Deposition of pigments
E. Pathologic calcifications
a. Dystrophic calcification
b. Metastatic calcification
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